Link Layer Discovery Protocol (LLDP)

Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer protocol defined in IEEE standard 802.1AB. Just like Cisco’s CDP, LLDP is used by network devices to advertise their identity, capabilities, and neighbors on a local Ethernet network. However, since LLDP is an open standard, it has one big advantage over CDP – it can be used on non-Cisco devices.

LLDP is disabled by default on Cisco devices. To enable it, use the lldp run command in the config mode:

R1(config)#lldp run

To display information about the LLDP neighbors, run the show lldp neighbors command:

This command displays information about whether LLDP is active on the device, the frequency of LLDP transmissions, the holdtime for packets being sent, and the delay time for LLDP to initialize on an interface.

You can also configure whether you would like your device to send or receive LLDP packets on a particular interface using the no lldp transmit and no lldp receive interface mode commands. For example, to only receive LLDP packets on the Gi0/0 interface, I would use the following command to disable the sending of LLDP packets: